1. Field of the Invention
The present invention relates to equipment for manufacturing semiconductor devices, and more particularly, to a process chamber used in the manufacture of semiconductor devices, capable of reducing contamination by particulates.
2. Description of the Related Art
In general, integrated circuits (ICs) are manufactured on semiconductor wafers formed of, for example, silicon. During the manufacture of the ICs, a series of steps, for example, photo masking, deposition of material layers, oxidation, nitridation, ion implantation, diffusion and etching, are conducted to obtain a final product. Most of these steps are carried out in a process chamber. Thus, reducing contamination by particulate in the process chamber has been recognized as a critical factor for determining the quality of a semiconductor device. Particulates are generated in a process chamber depending on the structure of the process chamber, the material used to form the chamber, and the types of reaction gases used in the chamber. In general, the process chamber is contaminated by particulates due to the following two reasons.
The first reason, which usually occurs in a process chamber used for etching, is the difference in temperature between edge rings (or focus rings) near a semiconductor wafer and the parts from which the process chamber is constructed. The second reason, which usually occurs in a process chamber used for a deposition process, is the unsmooth flow of a reaction gas near guide rings for guiding the edge of a semiconductor wafer.
FIG. 1 is a view illustrating the generation of particulates in a process chamber during an etching process. In detail, FIG. 1 is a sectional view illustrating an electrostatic chuck supporting a semiconductor wafer in a conventional process chamber for an etching process using plasma. FIG. 2 is an enlarged view of the edge (portion A) of the semiconductor wafer shown in FIG. 1, and FIG. 3 is a plan view of FIG. 1.
Referring to FIG. 1, an electrostatic chuck 20 holds a semiconductor wafer 10 using electrostatic adsorption. Although not shown in FIG. 1, a power supply for supplying a high voltage is connected to the electrostatic chuck 20 to induce static electricity. Lift pins 21 for moving the semiconductor wafer 10 up and down when loading or unloading the semiconductor wafer 10, pass through the center of the electrostatic chuck 20. The lift pins 21 are in contact with a support plate 22 installed below the electrostatic chuck 20. The support plate 22 moves upwards in response to force applied by an external lifter (not shown), in a direction indicated by an arrow 23. The lift pins 21 move upwards in response to upward movement of the support plate 22. Then, the lift pins 21 protrude past the surface of the electrostatic chuck 20, and the semiconductor wafer 10 supported by the lift pins 21 is separated from the surface of the electrostatic chuck 20.
Edge rings 24 are installed at the upper edges of the electrostatic chuck 20 to fix the semiconductor wafer 10. As shown in FIGS. 2 and 3, the edge ring 24 is separated from the edge of the semiconductor wafer 10 by a small gap 25. Also, there is a space 26 between part of the surface of the edge ring 24 and the periphery of the bottom surface of the semiconductor wafer 10. Also, a coupling ring 27 made of aluminum (Al) is interposed between the edge ring 24 and the electrostatic chuck 20. The semiconductor wafer 10 is surrounded by a focus ring 28. The focus ring 28 draws a plasma forming region to the edge of the semiconductor wafer 10 during the etching process, such that the plasma forming region is uniformly formed across the semiconductor wafer 10.
However, in such a conventional process chamber, plasma enters into the small gap 25 between the edge ring 24 and the edge of the semiconductor wafer 10, and thus the bottom surface of the semiconductor wafer may be etched. Polymers, which are byproducts generated by the etching, adhere to the bottom surface of the semiconductor wafer 10 and bind the edge ring 24 to the electrostatic chuck 20. When the edge ring 24 is separated from the electrostatic chuck 20 for repair and maintenance after the process is completed, the edge ring 24 can be broken due to it being bound to the electrostatic chuck 20 by the polymer.
When the etching is repeated several times, the edge ring 24 is etched along its inner circumference, so that the gap between the edge ring 24 and the semiconductor wafer 10 becomes wider. As a result, the edge ring 24 strikes against the edge of a platen zone of the semiconductor wafer (portion B of FIG. 3), so that a part of the semiconductor wafer 10 can be broken.
FIG. 4 is another view illustrating the generation of particulates in a process chamber used for an etching process. In detail, FIG. 4 is a sectional view of an electrostatic chuck 20 in which a focus ring 40 is included but not the edge ring shown in FIG. 3.
Referring to FIG. 4, a semiconductor wafer 10 is held by an electrostatic force produced by an electrostatic chuck 20, through which lift pins 21 are inserted. An annular focus ring 40 is arranged around the edge of the electrostatic chuck 20. The focus ring 40 draws a plasma forming region to the edge of the semiconductor wafer 10 during the etching process, such that the plasma forming region is uniformly formed across the semiconductor wafer 10. Further, the focus ring 40 acts as an edge ring, thereby preventing the semiconductor wafer 10 from deviating from its original position.
The upper part of the focus ring 40 is rounded, and the height of the focus ring is higher than the surface of the semiconductor wafer 10. Most of the polymers generated in the process chamber accumulate on the protruding top of the focus ring 40. Here, the amount and type of accumulated polymer varies according to the material forming the metal layer to be etched, and the distribution in temperature in the reaction chamber. For example, if a metal layer to be etched is formed of tungsten (W), an etching gas used for etching the metal layer, for example, SF6, reacts with the Al component of the process chamber and increases the concentration of Al in the process chamber, thereby generating floating particulates of AlXFY. Also, if a metal layer to be etched is formed of Al, an etching gas used for etching the metal layer, for example, Cl2 or BCl3, generates polymers of AlXClY. Such polymers lie on the protruding portion of the focus ring 40, which is the farthest away from a heat source (not shown), and may fall onto the semiconductor wafer 10 due to a change in internal pressure, thereby causing the process to fail.
FIG. 5 is a sectional view illustrating the generation of particulates in a process chamber used for a deposition process. FIG. 5 shows a wafer support portion of a process chamber for chemical vapor deposition (CVD). FIG. 6 is an enlarged view of the portion C of FIG. 5.
Referring to FIGS. 5 and 6, a semiconductor wafer 10 is seated on a wafer chuck 50, and a heater 51 is placed below the wafer chuck 50. The semiconductor wafer 10 is guided by an annular guide ring 52 placed around the edge of the wafer chuck 50. However, because a space d between the guide ring 52 and the wafer chuck 50 is very narrow, a reaction gas is stagnant in the space d and does not flow smoothly therein. As a result, the reaction gases staying in the space d react with each other abnormally, which results in the growth of an undesirable material layer 53. The material layer 53 may undesirably contaminate the wafer 10.
As described above, a process chamber used for etching or deposition produces particulates for various reasons, increasing the likelihood of failure of the semiconductor devices on wafer 10. Thus, it would be desirable to prevent such a failure by eliminating factors which may cause the generation of particulates in the process chamber during the manufacturing of the devices.
Consistent with the present invention, a process chamber for use in the manufacture of a semiconductor device, changes the structure or material of the process chamber to suppress generation of particulates.
In one aspect, a process chamber used in the manufacture of semiconductor device for etching a material on a semiconductor wafer using plasma includes an electrostatic chuck for holding the semiconductor wafer, and an annular edge ring which surrounds a side of the semiconductor wafer on the electrostatic chuck to prevent the semiconductor wafer from departing from its original position. The distance between the side of the semiconductor wafer and the first side is preferably less than 0.15 mm.
In another aspect, a process chamber used in the manufacture of a semiconductor device for etching a material on a semiconductor wafer using plasma includes an electrostatic chuck for holding the semiconductor wafer, and an annular focus ring which surrounds the side of the semiconductor wafer on the electrostatic chuck to prevent the semiconductor wafer from departing from its original position and to make the plasma distribution uniform by drawing the plasma. The annular focus ring has a first side which faces the side of the semiconductor wafer and contacts the side of the semiconductor wafer.
In another aspect, a process chamber used in the manufacture of a semiconductor device for etching a material on a semiconductor wafer using plasma includes an electrostatic chuck for holding the semiconductor wafer, a gas supply conduit, installed facing the upper surface of the semiconductor wafer, for supplying reaction gases to the upper space of the semiconductor wafer, wherein the gas supply conduit formed is slanted at a first angle with respect to the vertical direction, such that relatively more reaction gases are provided to a center of the semiconductor wafer than to a periphery of the semiconductor wafer, and a radio frequency power source for forming plasma in the upper space of the semiconductor wafer by ionizing the supplied reaction gases.
In another aspect, a process chamber used in the manufacture of a semiconductor device for etching a material layer on a semiconductor wafer using plasma includes an electrostatic chuck for holding the semiconductor wafer, a slit valve, attached to a sidewall of the process chamber and separated by a first distance from the electrostatic chuck, having a wafer transfer path through which the semiconductor wafer placed above the electrostatic chuck can be loaded or unloaded in the horizontal direction from or to the outside of the process chamber, wherein the temperature of the slit valve is maintained at a higher temperature than the sidewall of the process chamber during an etching process.
In another aspect, a process chamber used in the manufacture of a semiconductor device for depositing a material layer on a semiconductor wafer includes an electrostatic chuck for holding the semiconductor wafer, a heater installed below the wafer chuck, for supplying heat, and a guide ring for guiding the semiconductor wafer, the guide ring installed at the edge of an upper surface of the wafer chuck and separated from the chuck by about 15-25 mm.